IgAP has been the subject of intensive study since its discovery in the human body. It has been found that IgAP is secreted by pathogenic bacteria. The enzyme has been implicated in the diseases caused by these bacteria, namely gonorrhea, meningitis and influenza. The substrate of IgAP is IgA1. IgAP hydrolyzes IgA1 at a highly specific site that differs with the bacterial source of enzyme. IgA1 is naturally secreted in the human body by urogenital membranes. It has been observed that the amount of IgA1 on these membranes rises in response to infection (Mulks, et al., J. Infect. Dis. (1984) 150: 734-44). Although the role of IgAP in pathogenicity is not clear, it has been postulated that this increase in level is a natural defense mechanism of the body to bacteria which secrete IgAP.
The study of IgAP and its reaction with IgA1 would be aided by a rapid, simple assay for the enzyme. Current methods are cumbersome and time-consuming. Immunoelectrophoresis is a sophisticated technique which separates reaction products according to size and charge and then identifies them with anti-sera (Plaut, et al (1974) Adv. Exp. Med. Biol., 45: 245-249; Male C. J. (1979) Inf. Immun., 26: 254-261). SDS-PAGE analysis of 125I-labeled IgA1 is a sensitive technique, but is also time consuming (Blake, et al. (1979) J. Infect. Dis., 139: 89-92; Blake and Swanson (1978) Inf. Immun., 22: 350-358) Lindahl reports an assay utilizing IgA-binding protein from Group A streptococci which is useful under laboratory conditions but this method is also limited by time and labor requirements (Lindahl, L. (1981) J. Clin. Microbiol., 13: 991-993).
Accordingly, a rapid, simple assay of IgAP and its substrate IgA1 has been sought. A simple assay would allow detection of bacteria which secrete the enzyme and make possible early diagnosis of disease.